Pakistan's army launched raids and arrested suspects on Monday (Mar 28) after a Taliban suicide bomber targeting Christians over Easter killed 72 people, including many children in a park crowded with families.

Hundreds were also injured when explosives packed with ball bearings ripped through the crowds near a children's play area in the park in the eastern city of Lahore, where many had gathered on Sunday to celebrate Easter.

Anguished families spent Easter Monday burying their dead. "I tried to pump my son's chest and give him CPR but he was no more. He died right in front of me," Javed Bashir told AFP as relatives wailed at his son Mutahir's funeral.

"My son, my son, nobody should lose their sons," sobbed the mother of another victim as other women restrained her.

A spokesman for the Jamaat-ul-Ahrar faction of the Tehreek-e-Taliban Pakistan told AFP the group had carried out the attack as "Christians are our target", and vowed more assaults on schools and colleges. They later posted a picture of the man they said carried out the bombing, Salahuddin Khorasani.

The attack was the worst so far this year in a country grimly accustomed to atrocities, and will further undermine fractious inter-religious ties in the Muslim-majority nation.

In response the country's powerful army announced it had carried out raids in Lahore as well as in Faisalabad and Multan, two other major cities in Punjab province. More were planned.

"Number of suspect terrorists and facilitators arrested and huge cache of arms and ammunition recovered," army spokesman Asim Bajwa tweeted.

Prime Minister Nawaz Sharif vowed in a televised address on Monday evening to avenge the attack. "Terrorists cannot dent our resolve. Our struggle will continue until the complete elimination of the menace of terrorism," Sharif said.

A spokesman from his office said the prime minister would no longer be attending the Nuclear Security Summit to be held in Washington this week.

Witnesses told of children screaming as people carried the injured in their arms in the aftermath of the attack, while frantic relatives searched for loved ones.

Rescue spokeswoman Deeba Shahbaz said the death toll had risen to 72 Monday, with 29 children among the dead. Bits of human flesh and torn cloth could be seen Monday around the bloodstained swings and merry-go-round.

Authorities said the park had seen a surge of visitors thanks to Easter and the warm spring weather. Some 8,000 people were there when the bomb was detonated in the early evening, park officials said.

"The militants went for a softer target because there was tight security for churches in Lahore," said Cecil Shane Chaudhry, executive director of the National Commission for Justice and Peace, a Christian organisation.

MOURNING PERIOD

There were frenzied scenes at hospitals in the immediate aftermath, with staff treating casualties on floors and in corridors as officials tweeted calls for blood donations.

Lahore's top administration official Muhammad Usman said around 100 of the wounded were either treated at the scene or quickly discharged. He said a further 180 had been admitted to hospital.

Schools and other government institutions were open Monday but three days of mourning were announced in Punjab.

On Monday evening around 100 citizens including nurses and nuns gathered at the site to light candles and lay flowers for the dead. They also chanted slogans such as: "Friends of the Taliban are traitors."

The US has labelled the bombing "cowardly", while the Vatican called it "fanatical violence against Christian minorities" and UN chief Ban Ki-moon called for Islamabad to protect religious minorities.

Christians make up an estimated 1.6 per cent of Pakistan's 200 million people and have long faced discrimination.

Twin suicide attacks against churches in Lahore killed 17 people in March last year, sparking two days of rioting by thousands of Christians.

The country is still scarred by a Taliban assault on a Peshawar school in 2014 that killed 150 people, mostly children.

A military operation targeting insurgents was stepped up in response. Last year the death toll from militant attacks fell to its lowest since the Pakistani Taliban were formed in 2007.

But analyst Imtiaz Gul said despite significant progress in military operations against the Taliban, the group was still able to carry out major attacks.